Component and method for producing the same

ABSTRACT

A method and device are for anchoring fixed structural elements and, e.g., for anchoring electrodes for components, e.g., SOI wafer components, whose component structure is formed in a silicon layer on top of a substrate used as support. The fixed element may be mechanically connected to the substrate via at least one anchoring element made of an anchoring material and extending through the silicon layer. In the case of an SOI wafer, the anchoring element may extend through the silicon layer and the sacrificial layer of the SOI wafer. To this end, in the area of the surface of the fixed element, at least one recess is made in the silicon layer, which may extend through the entire silicon layer and the sacrificial layer down to the substrate. The recess may then be filled with an anchoring material, so that the fixed element is mechanically connected to the substrate via the anchoring element that is thereby created.

FIELD OF THE INVENTION

The present invention relates to a component, e.g., a sensor element,having a substrate used as support and a silicon layer, in which thecomponent structure is formed. The component structure includes at leastone fixed element, e.g., an electrode. Furthermore, the presentinvention relates to a method for manufacturing such a component.

BACKGROUND INFORMATION

In practice, many components and particularly sensor elements havingmovable structural elements are manufactured from so-called SOI (siliconon insulator) wafers. The structure of an SOI wafer normally includes amonocrystalline silicon layer connected to a silicon substrate via asilicon oxide layer. The component structure is formed in themonocrystalline silicon layer. Movable structural elements are exposedby removing the silicon oxide layer under these structural elements. Forthis reason, the silicon oxide layer is also called a sacrificial layer.The sacrificial layer is usually removed in an etching process, in whichnormally other parts of the component structure are undercut as well.This proves problematic in practice, especially with regard to fixedelements of the component structure such as electrodes, for example.That is to say, in sacrificial layer etching, the silicon oxideunderneath the electrodes is attacked as well. To date, it is onlypossible to ensure that the electrodes are mechanically anchored to thesilicon substrate if the electrodes have certain minimum dimensions, sothat they are not completely undercut during the etching of thesacrificial layer.

SUMMARY

An example embodiment of the present invention provides a device andmethod for anchoring fixed structural elements and, e.g., for anchoringelectrodes for components whose component structure is formed in asilicon layer on top of a substrate used as support. The foregoing maybe suitable for components manufactured from SOI wafers.

According to an exemplary embodiment of the present invention, the fixedelement of the component structure may be mechanically connected to thesubstrate via at least one anchoring element made of an anchoringmaterial and extending through the silicon layer. In the case of an SOIwafer, the anchoring element may extend through the silicon layer andthe sacrificial layer of the SOI wafer. To this end, in the area of thesurface of the fixed element, at least one recess may be made in thesilicon layer, which extends through the entire silicon layer and thesacrificial layer down to the substrate. The recess may then be filledwith an anchoring material, so that the fixed element may bemechanically connected to the substrate via the anchoring element thatis thereby created.

According to an exemplary embodiment of the present invention, it ispossible to connect fixed elements of the component structuremechanically to the substrate with the aid of anchoring elements. Thesole prerequisites for a reliable anchoring are that the anchoringmaterial is of sufficient mechanical strength and is not substantiallyattacked by the processes used in manufacturing the component, e.g., bythe etching of the sacrificial layer. An exemplary embodiment of thepresent invention may provide for the implementation of the smallestcomponent structures, which may be firmly connected to the substrate,and thus contributes to the miniaturization of components.

With regard to miniaturizing the component as much as possible andanchoring it reliably, the anchoring element may be situated essentiallyat the center of the surface of the fixed element. To this end, thesilicon layer and, in the case of an SOI wafer, the sacrificial layermay be patterned accordingly.

Anisotropic etching processes such as trenching, for example, aresuitable for pattering the silicon layer, since anisotropic etchingprocesses facilitate the creation of relatively deep yet narrowrecesses. In this manner, it is possible to minimize the space requiredfor the component structure. By continuing the anisotropic etchingprocess for patterning the silicon layer, the sacrificial layer may bepatterned accordingly. Alternatively, the sacrificial layer may also bepatterned using an isotropic etching process. Namely, during theisotropic etching of the sacrificial layer, the edge region of therecess in the silicon layer is undercut as well. The subsequent fillingof the recess extending through the silicon layer and the sacrificiallayer produces an anchoring element, which, on account of its barbedstructure as well as on account of the enlarged surface connecting it tothe substrate, may ensure a particularly strong anchoring of the fixedelement.

In an exemplary embodiment of the present invention, the anchoringmaterial may be deposited on the silicon layer after the silicon layerand the sacrificial layer have been patterned. This results in thegrowth of the anchoring material on the substrate in the area of therecess, which fills the recess and forms an anchoring element. Inaddition, the silicon layer may be coated with anchoring material. Thiscoating may be at least partially removed again, taking into account thefunction of the relevant structural elements of the component.

For an anchoring element that is used to anchor an electrode, anelectrically non-conductive anchoring material may be chosen to preventa short ciruit via the substrate of the component. Silicon carbide SiCand especially silicon-rich silicon nitride SiN may be provided in thisregard as anchoring materials. The above-mentioned coating withanchoring material may either extend only over a region of theelectrode's surface around the anchoring element or essentially over theentire surface of the electrode. In this case, however, at least onecontact hole for the electrode may be formed in the coating. The contacthole may be located outside of the region of the anchoring element, sothat the mechanical anchoring of the electrode and its electricalconnection are spatially decoupled.

In an exemplary embodiment of the present invention, a cap diaphragm maybe formed over the component structure, via which electrical contact maybe established with the electrodes of the component structure. The capdiaphragm may also be mechanically connected to the substrate via theanchoring elements.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the perspective representation of a sensor structureaccording to an exemplary embodiment of the present invention havingmovable and fixed elements.

FIG. 2 shows a sectional view of the sensor structure represented inFIG. 1 following the application of a second sacrificial layer forproducing a cap diaphragm.

FIG. 3 shows the sensor structure represented in FIG. 2 following thepatterning of the second sacrificial layer.

FIG. 4 shows the sensor structure represented in FIG. 3 following theapplication and patterning of a diaphragm layer.

FIG. 5 shows the sensor structure represented in FIG. 4 following theremoval of the second sacrificial layer.

DETAILED DESCRIPTION

An exemplary embodiment for a component according to the presentinvention represented in the figures is a sensor element 1 for recordingaccelerations.

Sensor element 1 may be manufactured from an SOI wafer containing amonocrystalline silicon layer 2, which may be connected via asacrificial layer 3 to a substrate 4, in this case a silicon substrate.Sacrificial layer 3 may be a silicon oxide layer. The sensor structuremay be formed in monocrystalline silicon layer 2 and may include movableelements 5, upon which an acceleration may act. The deflections ofmovable elements 5 from their rest position may be recorded with the aidof electrodes 6, which may be fixed elements of the sensor structure.

According to an exemplary embodiment of the present invention, eachelectrode 6 may be mechanically connected to substrate 4 via oneanchoring element 7. To this end, anchoring elements 7 may be positionedessentially at the center of the respective electrode surface and extendthrough entire silicon layer 2 and through sacrificial layer 3 down tosubstrate 4. Anchoring elements 7 may be formed of an electricallynon-conductive anchoring material. Silicon-rich silicon nitride SiN maybe used as anchoring material, since it is also resistant to the HFvapor etching of sacrificial layer 3, and since anchoring elements madeof SiN are of sufficient mechanical strength.

The production of the sensor structure represented in FIG. 1 may beginwith the creation of the recesses for anchoring elements 7 of electrodes6 in silicon layer 2. An anisotropic etching process, such as trenching,for example, may be used for this purpose. Subsequently, the siliconoxide in the region of these recesses may also removed. An anisotropicetching process may also be used for this purpose, since the edgeregions of the recesses in silicon layer 2 were not undercut. It is alsopossible to remove sacrificial layer 3 in the region of the recessesusing an isotropic etching process, so that the edge regions of therecesses in silicon layer 2 are undercut. This method may produceanchoring elements that extend in the area of sacrificial layer 3 tobelow silicon layer 2, thus creating a barbed structure.

The recesses, which may extend through entire silicon layer 2 andsacrificial layer 3 down to substrate 4, may be filled with theanchoring material. For this purpose, SiN may be deposited on siliconlayer 2 in a deposit step, so that it may grow on substrate 4 in thearea of the recesses. A sufficient amount of SiN may be deposited so asto subsequently close the recesses. At the same time, silicon layer 2may be coated with anchoring material. The SiN coating 8 may bepatterned such that it remains on the surfaces of the electrodes. Theelectrically insulating SiN on the surfaces of the electrodes allows foran electrically insulated mechanical connection of the electrodes to asubsequently produced diaphragm layer, which may be used for theelectrical connection of electrodes 6 of sensor element 1. To allow foran electrical contact between electrodes 6 and a connection in thediaphragm layer, a contact hole 9 may be formed for every electrode 6 incorresponding SiN coating 8. Contact opening 9 may be located away fromthe area of anchoring element 7 so as to decouple the electricalcontacting and the mechanical anchoring of electrode 6.

After anchoring elements 7 have been produced as described above, thefunctional sensor structure may be introduced into silicon layer 2,using an anisotropic etching process, for example, by trenching. In sodoing, both movable elements 5 as well as fixed elements of the sensorstructure, such as electrodes 6, may be defined. In a further processstep, the etching of the sacrificial layer movable elements 5 may beexposed. To this end, sacrificial layer 3 may be removed under movableelements 5 and electrodes 6. However, since the anchoring material isresistant to the HF vapor etching used for removing silicon oxide layer3, electrodes 6 remain mechanically firmly connected to substrate 4 viaanchoring elements 7.

The electrical connection of electrodes 6 of a sensor element 1, asrepresented in FIG. 1, may be effected via a thin-film diaphragm, whichmay additionally also seal the sensor structure. As an alternative tosuch thin-film packaging, the electrical connection may also be achievedvia a so-called cap diaphragm, which will be explained in more detailbelow in light of FIGS. 2 to 4.

To produce a cap diaphragm, a second sacrificial layer 11, which may bemade of silicon oxide, is applied to the sensor structure depicted inFIG. 1. Second sacrificial layer 11 may close the interstices betweenindividual elements 5 and 6, thereby creating a continuous surface, asshown in FIG. 2.

Subsequently, second sacrificial layer 11 may be patterned such thatopenings 12 and 13 are produced in sacrificial layer 11 wherever thediaphragm layer is to have direct contact with silicon layer 2 (openings12) or with SiN coating 8 (openings 13). FIG. 3 accordingly showsopenings 12 in the area of contact holes 9 and openings 13 in the areaof the coated surfaces of the electrodes.

A diaphragm layer 14 made of polysilicon or SiGe, for example, may thenbe produced on top of patterned second sacrificial layer 11. Followingthe application of a starting layer, polysilicon may simply be grownepitactically. Subsequently, diaphragm layer 14 may be patterned, whichin the case of a polysilicon layer may also be achieved by trenchetching. On the one hand, this patterning may produce openings 15 forthe sacrificial layer etching, during which at least second sacrificiallayer 11 and possibly also first sacrificial layer 3 may be removed. Onthe other hand, the patterning of diaphragm layer 14 may produceopenings 16, which electrically insulate the contact lead-throughsbetween functional silicon layer 2 and diaphragm layer 14 in the area ofcontact holes 9 from the remaining areas of diaphragm layer 14. Theseopenings 16 are referred to below as insulating trenches. Sensor element1 featuring the diaphragm layer patterned in this manner is representedin FIG. 4.

At this point, second sacrificial layer 11 and, if it has not yet beendone, also first sacrificial layer 3 may be removed again, in order toexpose movable elements 5 of the sensor structure. HF vapor etching maybe used for this purpose. As was already mentioned, the anchoringmaterial SiN is not attacked by HF vapor etching, so that electrodes 6remain mechanically rigidly connected both to substrate 4 as well as todiaphragm layer 14 via anchoring elements 7. FIG. 5 shows sensor element1 having a cap diaphragm 14 produced in this manner. On the one hand,cap diaphragm 14 is in immediate contact with electrodes 6 via contactholes 9, thus enabling their electrical connection. On the other hand,cap diaphragm 14 is mechanically connected to substrate 4 via SiNcoating 8 of the electrode surfaces and via anchoring elements 7, sothat cap diaphragm 14 is anchored as well.

An electrode 6, electrically connected via cap diaphragm 14, may beseparated from the remaining areas of cap diaphragm 14 by an insulatingtrench 16, in order to achieve the electrical separation of electrode 6.Anchoring element 7 prevents electrode 6 from being completely undercutvia insulating trench 16 and other perforations and thus from beingdetached from substrate 4. Positioning contact hole 9 and anchoringelement 7 in different areas of electrode 6 spatially decouples themechanical anchoring and the electrical connection, so that nocomplications are to be expected from the insulating trench.

The foregoing may allow for the mechanical anchoring of fixed structuralelements such as electrodes, for example, to the substrate. This isachieved with the aid of anchoring elements which may be introduced intothe fixed structural elements and which may be made of a materialresistant to the etching of the sacrificial layer. In the case of ananchoring of electrodes, the anchoring material may also be electricallyinsulating, in order to allow for a spatial separation of anchoring andelectrical contacting. Silicon-rich nitride or SiC may be provided asanchoring materials.

1-19. (canceled)
 20. A component, comprising: a substrate configured asa support; and a silicon layer in which a component structure is formed,the component structure including at least one fixed elementmechanically connected to the substrate via at least one anchoringelement made of an anchoring material and extending through the siliconlayer.
 21. The component of claim 20, wherein the silicon layer isconnected to the substrate via a sacrificial layer, the fixed elementmechanically connected to the substrate via at least one anchoringelement extending through the silicon layer and the sacrificial layer.22. The component of claim 20, wherein the anchoring element is locatedessentially at a center of a surface of the fixed element.
 23. Thecomponent of claim 21, wherein the anchoring element includes a barbedstructure and extends in an area of the sacrificial layer to below thesilicon layer.
 24. The component of claim 20, wherein the anchoringelement is configured to anchor an electrode and the anchoring materialis electrically non-conductive.
 25. The component of claim 24, wherein asurface of the electrode in at least one region around the anchoringelement includes a coating made of the anchoring material.
 26. Thecomponent of claim 25, wherein the coating extends essentially over anentire surface of the electrode, and at least one contact hole is formedin the coating for the electrode, the contact hole located outside theregion around the anchoring element.
 27. The component of claim 24,wherein a cap diaphragm is formed on top of the component, the at leastone electrode is electrically contacted via the cap diaphragm and thecap diaphragm is mechanically connected to the substrate via theanchoring element.
 28. The component of claim 20, wherein the anchoringmaterial includes one of (a) silicon nitride and (b) silicon carbide.29. A method for manufacturing a component including at least one fixedelement produced in a silicon layer, the silicon layer connected to asubstrate via a first sacrificial layer, comprising: (a) making at leastone recess in the silicon layer in an area of a surface of the fixedelement, the recess extending through the entire silicon layer and thefirst sacrificial layer down to the substrate; and (b) filling therecess with an anchoring material to mechanically connect the fixedelement to the substrate via an anchoring element that is therebycreated.
 30. The method of claim 29, wherein the recess in the siliconlayer is made in the making step in an anisotropic etching process. 31.The method of claim 29, further comprising removing the firstsacrificial layer in an area of the recess in an anisotropic etchingprocess.
 32. The method of claim 31, wherein the anisotropic etchingprocess includes undercutting an edge region of the recess in thesilicon layer.
 33. The method of claim 29, further comprising:depositing the anchoring material on the silicon layer to grow on thesubstrate in an area of the recess and fills the recess; and at leastpartly removing an anchoring material coating of the silicon layercreated by the depositing of the anchoring material.
 34. The method ofclaim 29, further comprising: forming a cap diaphragm on the component;producing a second sacrificial layer having a continuous surface on topof the component that is defined in the silicon layer and in which atleast one electrode having the at least one anchoring element is alreadyformed; patterning the second sacrificial layer; removing the secondsacrificial layer in an area of the anchoring element and in an area ofat least one contact point on the surface of the electrode; producing adiaphragm layer on top of the patterned second sacrificial layer;patterning the diaphragm layer; creating openings for removing thesecond sacrificial layer; creating openings through which an electricalconnection of the electrode to the diaphragm layer is electricallyinsulated from remaining areas of the diaphragm layer; and removing atleast the second sacrificial layer.
 35. The method of claim 34, whereinthe diaphragm layer is produced in the diaphragm layer producing stepfrom one of (a) polysilicon and (b) SiGe.
 36. The method of claim 34,wherein the diaphragm layer is grown epitactically from polysilicon. 37.The method of claim 36, wherein the diaphragm layer is patterned usingtrench etching.
 38. The method of claim 34, wherein the secondsacrificial layer is produced in the second sacrificial layer producingstep from silicon oxide.
 39. The component of claim 20, wherein thecomponent is configured as a sensor element.
 40. The component of claim20, wherein the at least one fixed element includes an electrode. 41.The method of claim 29, wherein the component is configured as a sensorelement.
 42. The method of claim 29, wherein the at least one fixedelement includes an electrode.
 43. The method of claim 30, wherein therecess in the silicon layer is produced by trenching.
 44. The method ofclaim 31, wherein the first sacrificial layer in the area of the recessis removed by trenching.
 45. The method of claim 34, wherein openingsare created for removing the second and also the first sacrificiallayer.
 46. The method of claim 34, wherein the second sacrificial layeris removed using HF vapor etching.